Capacitive proximity switch

Abstract

A capacitive proximity switch for detecting the change in the capacitance relative to a setpoint capacitance by the approach or retreat of an object in the sensitive area of a proximity switch, especially for use in the door handle of a motor vehicle, provides reliable error detection and error suppression at a fundamentally high sensitivity of the capacitive proximity switch by utilizing an evaluation unit that evaluates a measured value of the change in capacitance over time and depending on the time behavior of the measured value activates changes the operating threshold from a first threshold (which can be caused by a false object coming into or out of the sensitive area of the proximity switch) to a higher second threshold which can be reached only at a relatively greater change in capacitance caused by a target object coming into or out of the sensitive area of the proximity switch.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The invention relates to a capacitive proximity switch for detecting the change in the capacitance relative to a setpoint capacitance Cset by the approach or retreat of an object in the sensitive area of a proximity switch, especially for use in the door handle of a motor vehicle, with an electrode system which has at least one response electrode and with a switching output, the measured value which corresponds to the change in capacitance being compared to an operating threshold S1 and at the switching output a switching signal being produced depending on the measured value.[0003]2. Description of Related Art[0004]As is recognized, capacitive proximity switches respond when the capacitance between the response electrode and a reference electrode reaches or exceeds a certain value, specifically because the response electrode approaches an object which for its part is galvanically or capacitively connected to the referen...

AI Technical Summary

Benefits of technology

[0018]In view of the foregoing, a primary object of the present invention is to provide a capacitive proximity switch with reliable error detection or error suppression, the error suppression being designed not to lead to a general reduction of the sensitivity of the capacitive proximity switch. In the specific application, the object is especially to ensure reliable rain detection or rain suppression, and to make available a sufficient lead time due to the high sensitivity of the capacitive proximity switch.

Problems solved by technology

For the described activation, this means that the second operating threshold is activated when rain is recognized by the capacitive proximity switch or by the evaluation unit, so that any small change in capacitance which has been measured by the capacitive proximity switch and which is caused by raindrops no longer leads to activation of the switching output, and thus, to an authorization query which is associated with increased current consumption by the identification receiver.

The resulting delayed unlocking of the door lock is a minor disruption in the ease of operation which, however, only occurs intermittently so that this minor disadvantage can be accepted.

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